fix: private helm registry (#7)

Fixing the setup for the private helm registry. Instead of providing the "host" as the name of the field would suggest, one has to provide a full URL, which also becomes clear, when reading the [documentation](https://docs.renovatebot.com/getting-started/private-packages/).

Reviewed-on: #7
Reviewed-by: branch-buddy <branch-buddy@t00n.de>
Co-authored-by: Timo Behrendt <t.behrendt@t00n.de>
Co-committed-by: Timo Behrendt <t.behrendt@t00n.de>

helm.json

@@ -13,5 +13,13 @@
   "helmfile": {
     "enabled": true,
     "addLabels": ["deps", "helm"]
-  }
+  },
+  "hostRules": [
+    {
+      "matchHost": "https://gitea.t000-n.de/api/packages/t.behrendt/helm",
+      "hostType": "helm",
+      "username": "{{ secrets.HELM_REGISTRY_USER }}",
+      "password": "{{ secrets.HELM_REGISTRY_PASSWORD }}"
+    }
+  ]
 }